1. Technical Field of the Invention
The present invention relates to a control apparatus that controls both a fuel injection system and an exhaust gas cleaning system for an internal combustion engine.
2. Description of the Related Art
There is disclosed, for example in Japanese Patent First Publication No. H9-222009, an exhaust gas cleaning system which includes a fuel adding device to add fuel to the exhaust gas from an internal combustion engine. Specifically, the fuel adding device is provided to inject fuel into an exhaust passage of the engine, thereby causing a filter, which collects the particulate matter contained in the exhaust gas, to be regenerated.
On the other hand, there is known a fuel injection system for an internal combustion engine which includes a fuel pump, a plurality of fuel injectors, and a control apparatus. The fuel pump pressurizes and supplies fuel. The fuel injectors inject the fuel supplied from the fuel pump into cylinders of the engine, respectively. The control apparatus controls operation of the fuel injection system. For example, the control apparatus controls the quantity of fuel pressurized and supplied by the fuel pump and the quantities of fuel injected by the fuel injectors, thereby making the engine operate in a desired operating condition. Furthermore, the control apparatus also diagnoses whether the fuel injection system is in a normal or abnormal condition.
However, when the above-described exhaust gas cleaning system and fuel injection system are used together and a common control apparatus controls both the systems, the operation of the fuel adding device may interfere with the control by the control apparatus of the fuel injections by the fuel injectors or/and with the diagnosis by the control apparatus of the fuel injection system. Consequently, it may become impossible for the control apparatus to reliably make the engine operate in a desired operating condition or/and to accurately diagnose the fuel injection system.